He lived in the wintery port city of Keterburg, along with Dist, who was then known as Saphir, the future Emperor Peony IX, and his own younger sister, Nephry. In his youth, he was, as described by his sister, a "devil" who was highly adept in casting fonic artes; his sister saw him as one who did not understand the significance of life or perhaps that anything but himself could be sentient, and therefore he enjoyed killing monsters through fonic artes even adults found difficult. When he was nine he created the process known as fomicry, the science of extracting data from an existing entity to produce a perfect copy known as a 'replica'. His first attempt was when his sister, Nephry, broke her favorite doll, at which point Jade created a replica to soothe her tears.
He was, however, significantly changed by his teacher, Dr. Gelda Nebilim, a healer who commanded the Seventh Fonon, which Jade could not command himself. Though he had great respect for his teacher, Jade attempted to control the Seventh Fonon, but instead unleashed a power beyond his control that resulted in the death of Nebilim. As Nebilim lay dying, Jade extracted her data and created a replica of her, though rather than resurrecting his beloved teacher, he only succeeded in creating a monster which he found himself forced to seal away due to its destructive nature. Despite playing a minor role in the story as a whole, Nephry reveals a great deal of Jade's backstory, as well as the details of his relationship with his former friend, Dist. According to her, Jade began fomicry at the age of nine when he created a replica of her favorite doll, which had broken. The experience of fomicry in action had a traumatic effect on the young Nephry, as evidenced when she later remarks to the party that she "felt something abnormal in his way of thinking," also referring to him as a devil. Prior to the beginning events in Keterburg, Nephry and Jade had not spoken since her wedding.